A teenager accused of sexually assaulting a 15-year-old girl during a satanic ritual, before disfiguring her body and killing her, is on trial in the US state of Texas.

Jose E. Reyes, 18, allegedly killed Corriann Cervantes, 15, in a vacant apartment in southeast Houston in February this year.

A 16-year-old boy who has also been charged over the incident is expected to stand trial in January.

On the night of the incident, the two boys allegedly engaged in consensual sex with Cervantes before brutally attacking her.

In opening statements in court today, prosecutors said the two boys hoped to form a pact with the devil by disfiguring Cervantes.

During the ritual, the boys are alleged to have strangled her, carved an inverted crucifix into her stomach, and gouged her eyes out. Remnants of a toilet lid used to hit her were found embedded in her skin.

Her body was later discovered in an apartment on 8 February.

If Reyes is found guilty, he faces a life sentence but would be eligible for parole after 30 years.

"Whether or not the devil was involved, what happened in that apartment was sadistic and inhumane," Assistant Harris County District Attorney John Jordan told jurors, the Houston Chronicle reported.

Defense attorney Jerald Graber told the Houston Chronicle the defense team would “zealously represent” the teen.

In an exclusive interview with ABC13 Eyewitness News, Reyes admitted that he and his alleged accomplice took drugs with Cervantes on the night in question, but said they left before she died.

Reyes denied he was a Satanist and said he was a Christian, but admitted to being curious about the devil when he was younger.